What is the primary reason divers should track residual nitrogen time?

Tracking residual nitrogen time is crucial primarily to avoid decompression sickness. When a diver descends and ascends during a dive, they absorb nitrogen from the breathing gas at higher pressures. If a diver ascends too quickly or does not allow sufficient time for that absorbed nitrogen to safely leave the body, it can form bubbles in the bloodstream, leading to decompression sickness, also known as "the bends."

By monitoring the amount of time spent at various depths and the total nitrogen saturation in their system, divers can manage their ascent profiles more safely. This helps ensure that they allow enough time for nitrogen to off-gas before surfacing, effectively minimizing the risk of decompression-related injuries. Maintaining proper residual nitrogen time awareness is a key practice in safe diving protocols.

Other options, while important in their own right—such as determining optimal dive gear, enhancing underwater navigation, and improving buddy communication—do not address the critical safety concern that residual nitrogen tracking aims to mitigate.